title: The Arabidopsis calcium sensor calcineurin B-like 3 inhibits the 5'-methylthioadenosine nucleosidase in a calcium-dependent manner.
abstract: Calcineurin B-like (CBL) proteins represent a unique family of calcium sensors in plant cells. Sensing the calcium signals elicited by a variety of abiotic stresses, CBLs transmit the information to a group of serine/threonine protein kinases (CBL-interacting protein kinases [CIPKs]), which are currently known as the sole targets of the CBL family. Here, we report that the CBL3 member of this family has a novel interaction partner in addition to the CIPK proteins. Extensive yeast two-hybrid screenings with CBL3 as bait identified an interesting Arabidopsis (Arabidopsis thaliana) cDNA clone (named AtMTAN, for 5'-methylthioadenosine nucleosidase), which encodes a polypeptide similar to EcMTAN from Escherichia coli. Deletion analyses showed that CBL3 utilizes the different structural modules to interact with its distinct target proteins, CIPKs and AtMTAN. In vitro and in vivo analyses verified that CBL3 and AtMTAN physically associate only in the presence of Ca(2+). In addition, we empirically demonstrated that the AtMTAN protein indeed possesses the MTAN activity, which can be inhibited specifically by Ca(2+)-bound CBL3. Overall, these findings suggest that the CBL family members can relay the calcium signals in more diverse ways than previously thought. We also discuss a possible mechanism by which the CBL3-mediated calcium signaling regulates the biosynthesis of ethylene and polyamines, which are involved in plant growth and development as well as various stress responses.
authors.affiliation: Department of Molecular Biology, Sejong University, Seoul 143-747, Korea.
authors.forename: Seung-Ick
authors.initials: SI
authors.lastname: Oh
authors.forename: Jimyeong
authors.initials: J
authors.lastname: Park
authors.forename: Sunhee
authors.initials: S
authors.lastname: Yoon
authors.forename: Yungyeong
authors.initials: Y
authors.lastname: Kim
authors.forename: Soojin
authors.initials: S
authors.lastname: Park
authors.forename: Migyeong
authors.initials: M
authors.lastname: Ryu
authors.forename: Min Jung
authors.initials: MJ
authors.lastname: Nam
authors.forename: Sung Han
authors.initials: SH
authors.lastname: Ok
authors.forename: Jeong-Kook
authors.initials: JK
authors.lastname: Kim
authors.forename: Jeong-Sheop
authors.initials: JS
authors.lastname: Shin
authors.forename: Kyung-Nam
authors.initials: KN
authors.lastname: Kim
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D002118:Calcium / Q000494:pharmacology*; D020013:Calcium Signaling / Q000502:physiology; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D005966:Glucuronidase / Q000032:analysis; D049452:Green Fluorescent Proteins / Q000032:analysis; D008969:Molecular Sequence Data; D019697:Onions / Q000235:genetics; D025941:Protein Interaction Mapping; D011683:Purine-Nucleoside Phosphorylase / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000032:analysis; D016415:Sequence Alignment; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; C484079:CBL3 protein, Arabidopsis; D002135:Calcium-Binding Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D011683:Purine-Nucleoside Phosphorylase; C021784:5'-methylthioadenosine phosphorylase; D005966:Glucuronidase; D002118:Calcium